Portal trace detection systems for detection of imbedded particles

ABSTRACT

A portal trace detection apparatus is provided for detecting minute particles of interest, such as traces of narcotics, explosives and other contraband. The apparatus includes a portal through which a human suspect will pass. A detection apparatus is disposed at least partly in the ceiling of the portal, and hence above the human subject in the portal. Particles of interest will be entrained in the human thermal plume that exists in the boundary adjacent the suspect, and will flow upwardly from the suspect to the detection apparatus in the ceiling of the portal. The ceiling is coated with an anti-static material so that particles are more likely to flow towards the detector and less likely to be affixed electrostatically to the ceiling.

This application is a divisional of U.S. patent application Ser. No.10/774,004 filed Feb. 6, 2004, which is a divisional of U.S. patentapplication Ser. No. 10/033,874, filed Dec. 20, 2001, now issued as U.S.Pat. No. 6,708,572.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject invention relates to a detection apparatus for dislodgingparticles from clothing and skin of a person and then testing thedislodged particles for the presence of substances of interest.

2. Description of the Related Art

Detection systems exist for detecting traces of materials, such asnarcotics and explosives. Such systems are marketed by Ion TrackInstruments, Inc. and are shown, for example, in U.S. Pat. No.5,491,337.

Prior art detection systems rely upon the fact that trace amounts ofcontraband will be transferred to the body of a person who handled thecontraband, and subsequently will be transferred from the body to anyarticle that the person may carry. These trace amounts of contraband maybe collected for analysis by wiping a small sheet of appropriatematerial across a purse, suitcase or other article that has been handledby a suspect. The prior art sheet then is inserted into a prior artdetection apparatus which tests for the presence of certain contraband.

Attempts have been made to provide such contraband testing withoutphysically contacting the suspect or articles that the suspect may betransporting. Several such prior art devices employ a portal throughwhich the suspect will walk. Most of these prior art devices create aflow of air in the portal in an effort to entrain the particles ofinterest in a continuously flowing air stream. The air stream then isdirected to a detector which attempts to identify the presence ofparticles of interest. Unfortunately, the prior art apparatus draws asignificant volume of air from outside the portal, and hencesubstantially dilutes the concentration of particles of interest in theair stream that is directed to the detector.

U.S. Pat. No. 6,073,499 shows a recent improvement with respect toportals for detecting the presence of contraband on a suspect. Moreparticularly, U.S. Pat. No. 6,073,499 discloses a portal detectionsystem that relies upon the fact that a boundary of air adjacent to ahuman being is heated by the body. The heated air in this boundary layeris less dense than air further from the suspect, and hence will flowupwardly. Thus, a human thermal plume is created naturally around thehuman suspect. Particles of interest will be entrained in this thermalplume and will rise upwardly around the body. The portal system shown inU.S. Pat. No. 6,073,499 relies upon this natural phenomena by providinga fan or other air flow generator at a location above the suspect andoperating at a speed to substantially match the airflow rate of thenaturally-occurring human thermal plume. Thus, the fan or other suchdevice shown in U.S. Pat. No. 6,073,499 merely directs the naturallyoccurring human thermal plume to a detector without drawing significantvolumes of ambient air into the detector. Thus, the concentration ofparticles of interest is significantly higher than the concentration inprior art portals that create a significant artificial airflow in aneffort to entrain and transport the particles of interest.

The prior art detection portal disclosed in U.S. Pat. No. 6,073,499 isparticularly effective for detecting trace amounts of contraband thatmay have been deposited on the skin of a suspect. However, microscopicparticles of contraband also are very likely to be trapped in theclothing of a suspect. The natural thermal plume existing in theboundary layer surrounding a human suspect may not be capable ofdislodging particles of interest from the clothing. Of course, most of ahuman suspect will be covered by clothing. Hence, the efficiency of thesystem disclosed in U.S. Pat. No. 6,073,499 may be limited somewhat bythe tendency of particles of interest to be trapped in the clothing ofthe human suspect passing through the portal.

Some prior art systems, including the system shown in U.S. Pat. No.6,073,499 suggest the use of air jets to dislodge particles of interestfrom clothing. However, air jets can create turbulence that may disruptthe efficient upward flow of air in the natural thermal plumesurrounding the human suspect. Additionally, air jets have the potentialof creating air flow patterns that will draw significant volumes of airfrom the ambient surroundings, thereby reducing the concentration of theparticles of interest in the flow of air directed to the detector.

In view of the above, an object of the subject invention to provide aportal trace detection system that is capable of detecting embeddedparticles, such as particles embedded in clothing of a human suspectpassing through the portal.

SUMMARY OF THE INVENTION

The subject invention is directed to a portal detection system thatrelies primarily upon the upwardly flowing human thermal plume. Theportal includes an inspection apparatus with an inlet disposed above thearea of the portal where the human suspect will stand. The inlet may bein communication with a fan or other such device for generating an airflow. Preferably, the fan or other such apparatus will operate togenerate an air flow that substantially matches the air flow rate in atypical human thermal plume. For example, the air flow rate in closeproximity to the human body is approximately 0.5 meter per second, andthe fan may function to substantially match this air flow speed andvolumetric rate of flow.

The portal of the subject invention may be similar to the portal shownin U.S. Pat. No. 6,073,499 in most relevant respects. However, theportal of the subject invention is supplemented by a plurality of airjets disposed at locations that will extend approximately from kneelevel to chest level of a typical human subject passing through theportal. Tests have shown that this area of the body carries mostcontamination after handling a contraband material.

The array of air jets preferably comprises a plurality of vertical linesof air jets disposed at a plurality of different sides on the portal anddirected inwardly and upwardly in the portal. For example, four verticallines of air jets may be disposed respectively at the corners of theportal. The air jets in each line may be separated from one another byabout 300 mm, and preferably are aligned to the vertical at an angle ofbetween 30°-60°.

The jets may be connected to a high pressure (40-100 psi) air supply andmay be operated sequentially by solenoid valves that are connected toand operated by a controller. Each jet is operative to deliver a shortpuff of air which disturbs the clothing of the human suspectsufficiently to release trapped particles. The air flow created by thejets necessarily disturbs the body plume somewhat, and hence conceivablycould cause a turbulence that could direct particles of interest out ofthe portal. However, the effect of the jets on the human thermal plumecan be minimized substantially by operating each jet only for a veryshort duration. Thus, each jet functions essentially like a smoke ringwith a local disturbance, but a minimum effect on air flow patterns inthe human thermal plume. Furthermore, the effect of the short puffs ofair produced by the jet can be used cooperatively with the human thermalplume by actuating the jets sequentially from bottom to top in each ofthe vertical arrays of jets. The jets preferably are switched on forabout 10-80 ms, and each level of jets is switched off before the nextlevel is switched on. It has been determined that longer periods ofoperation for the respective jets adversely affects the human thermalplume without significantly increasing the release of particles from theclothing of the human suspect passing through the portal.

The portal apparatus of the subject invention provides still a furtheradvantage. In particular, it has been determined that small danderparticles that are given off from the skin gradually migrate into theclothing. These dander particles can act as vapor traps for very lowvolatility materials, such as explosives and narcotics which may behidden under the clothing of under the human subject passing through theportal. These dander particles are released by the jets, and hencebecome entrained in the human thermal plume. More particularly, thedander particles effectively become tiny traps that are released by thejets and transported in the human thermal plume to the detection systemwhere the trapped vapors are desorbed. Thus, the incorporation of thejets into the portal detection system creates the possibility ofdetecting vapors that normally would be below the threshold ofsensitivity of the system.

It also has been determined that particles of interest often affixthemselves to the hood or ceiling of the portal due to staticelectricity, in much the same way that dust accumulates on a televisionscreen. This phenomenon can be reduced or eliminated by coating the hoodor ceiling with an anti-static material. Thus, fewer particles becomeaffixed to the hood, and sensitivity is increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a portal detection apparatus in accordancewith the subject invention.

FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A portal detection system in accordance with the subject invention isidentified generally by the numeral 10 in FIGS. 1 and 2. The portaldetection system 10 is similar to the portal detection system disclosedin U.S. Pat. No. 6,073,499. In particular, the portal detection system10 includes a portal 12 having a plurality of sidewalls 14, a plasticceiling or hood 16 and a passage 18 extending between the sidewalls 14and beneath the ceiling 16. The ceiling 16 preferably is made from orcoated with an anti-static material such as KYDEX T as manufactured byKleerdex. The anti-static material reduces or eliminates theelectrostatic accumulation of particles of interest on the ceiling, andhence improves sensitivity. The ceiling 16 includes an inlet with a fanfor producing an air flow that substantially matches the air flow rateprovided by the human thermal plume. The ceiling 16 further includes atleast portions of detection system 17. The detector of the subjectinvention is not disclosed herein. However, the detector may be an iontrap mobility spectrometer as disclosed in U.S. Pat. No. 5,491,337.Additionally, various structural and operational features of the portal12 are as disclosed in U.S. Pat. No. 6,073,499. The disclosures of thesetwo patents are incorporated herein by reference.

The apparatus 10 of FIGS. 1 and 2 further includes a plurality of airjets 20. The jets are arranged to define four linear jet arrays 22 withthe jets 20 in each array 22 being vertically aligned. The jets 20preferably are disposed in the portal 12 to extend from a lower locationapproximately at knee level (e.g., 1-2 feet from the ground) to an upperlocation approximately at chest level (e.g., 4-5 feet from the ground).Each jet 20 is disposed to direct a short puff of air inwardly andupwardly into the passage 18 of the portal 12. More particularly, asshown most clearly in FIG. 1, the jets 20 are aligned at an acute angleof approximately 30°-60° to the vertical. The jets communicate with asupply of high pressure air in the range of 40-100 psi and preferably 80psi. The jets include solenoid valves that communicate with and arecontrolled by a controller 24 to operate sequentially. Moreparticularly, the controller 24 functions to fire the respective jets 20sequentially from bottom to top. Each jet 20 is switched on for about10-100 ms, and preferably about 50 ms. Each jet 20 then is switched offfor about 100 ms before the next higher jet 20 is switched on. The jets20 function to disturb the clothing of the human subject in the passage18 sufficiently to dislodge particles of interest that may be trapped inthe clothing of the suspect. However, the short puffs of air arecontrolled to achieve minimum disruption and minimum dilution of thehuman thermal plume. The dislodged particles then are entrained in thehuman thermal plume that exists adjacent the human subject. The air inthe human thermal plume, including the particles of interest that aredislodged from the clothing are directed to the detector substantiallyas disclosed in U.S. Pat. No. 6,073,499.

In use, the suspect is instructed to enter the portal 12. Visual signalsor voice prompts will ask the suspect to remain in the portal 12 forabout 5-10 seconds. The jets 20 will then fire sequentially from bottomto top. More particularly, the four lower tier jets 20 will firesimultaneously for about 50 ms. There then will be a pause of about 100ms, and the four jets 20 in the second tier will fire for about 50 ms.This process will continue until the four jets 20 in the tip tier havefired. Particles displaced by the jets 20 will be entrained in the humanthermal plume and will flow naturally upward through the hood-shapedceiling 16. After about 5-10 seconds, the suspect will be instructed toexit the portal 12.

1. A portal trace detection system comprising a portal having aplurality of sidewalls and a passage between the sidewalls, a ceilingconnecting the sidewalls and disposed above the passage, a particledetection apparatus having an inlet in the ceiling and communicatingwith the passage for receiving air flowing upwardly in the portal andtowards the ceiling, at least the surface of the ceiling facing into thepassage comprising an anti-static material for reducing electrostaticaccumulation of particles of interest on the ceiling.
 2. The portaltrace diction system of claim 1, wherein the ceiling is formed from aplastic material coated with the anti-static material.
 3. The portaltrace detection system of claim 1, wherein the ceiling is formed fromthe anti-static material.
 4. The portal trace detection system of claim1, wherein the ceiling includes a concave surface facing into thepassage.
 5. The portal trace detections system of claim 1, furthercomprising a plurality of jets for directing air into the passage fordislodging particles from the suspect.
 6. A portal trace detectionsystem comprising a portal having a plurality of sidewalls and a passagebetween the sidewalls, a ceiling connecting the sidewalls and disposedabove the passage, a particle detection apparatus communicating with thepassage for receiving air flowing adjacent to a suspect in the passageof the portal, at least selected surface areas of the portal facing intothe passage comprising an anti-static material for reducingelectrostatic accumulation of particles of interest on surfaces of theportal facing into the passage.
 7. The portal trace detection system ofclaim 1, wherein the anti-static material is on the ceiling.
 8. Theportal trace detection system of claim 6, wherein the ceiling includes aconcave surface facing into the portal.
 9. The portal trace detectionsystem of claim 7, wherein the ceiling is formed from a plastic materialcoated with an anti-static material.
 10. The portal trace detectionsystem of claim 9, wherein the detector has an inlet in the ceiling.